Cohesion and Adhesion
Cohesion is the ability of water molecules to stick to each other (due to hydrogen bonds). Because of cohesion, water exists as a liquid under ordinary temperatures and pressure. You can see the cohesive properties of water in a water droplet. It is what allows water to form the bubble shape.
Water molecules that cling together at the surface exhibit what is called surface tension. The layer at the surface acts almost as a skin. This is how some insects are able to sit on top of the water. You can also see this by filling a cup to the very top and gently laying a paper clip or needle on the water. It will not break the surface of the water.
Water molecules that cling together at the surface exhibit what is called surface tension. The layer at the surface acts almost as a skin. This is how some insects are able to sit on top of the water. You can also see this by filling a cup to the very top and gently laying a paper clip or needle on the water. It will not break the surface of the water.
Adhesion is the ability of water molecules to cling to other polar surfaces. You can see in the picture on the right (above) how the water is sticking to the plant. The adhesive and cohesive properties of water allow for a very important process to take place in living organism such as plants. Plants have their roots anchored in the soil, where they absorb water. Water moves up the plant through the xylem (vascular tube) through a process called capillarity. Because water is cohesive, as water evaporates from the leaves, water is pulled up from the roots against the force of gravity. Adhesion allows the water to stick to the sides of the xylem and cohesion allows the water to stick to itself and thus pull more water up the plant.